Glow suppression in indicator tubes

ABSTRACT

An insulating shield is interposed between the anode cup and extending portions of cathode leads in a glow discharge indicator tube to prevent the spread of discharge along the leads. The leads pass through an aperture in the anode cup and shield.

United States Patent Inventor Frederick Gustav Adolf Haegele Exeter, South Devon, England 764,696

211 Appl. No. 221 Filed 2,990,061 McCauley 313/l09.5 3,005,922 313/109 5 3,303,375 2/1967 Klepp et al.... 313/109.5 3,067,354 12/1962 Peterson....................... 313/109.5X

Primary Examiner-Roy Lake Oct. 3, 1968 [45] Patented Feb. 9, 1971 [73] Assignee International Standard Electric Corporation New York, NY. a corporation of Ddaware Assistant Examiner- David [32] P io it O t, 12, 1967 Attorneys-C. Cornell Remsen, Jr., Walter J. Baum, Percy P. [33] Great Britain Lantzy, Philip M. Bolton, Isidore Togut and Charles L. [31 1 46,533/67 Johnson, Jr.

[54] GLOW SUPPRESSION IN INDICATOR TUBES 5 Claims, 2 Drawing Figs.

313/210, 313/219 ABSTRACT: An insulating shield is interposed between the [51] Int. 61/66, anode cup and extending portions of cathode leads in a glow discharge indicator tube to prevent the spread of discharge along the leads. The leads pass through an aperture in the anode cup and shield.

H0lk7/04 [50] 313/109.5, 210, 219, 332; 174/5056, 50.59

PATENTEU FEB 9 IQYI SHEET 1 OF 2 Inventor FREDERICK G. A. l/AEGELE Allqrne PATENTED FEB 9 I97! SHEET 2 BF 2 INVENTOR FREOERICK G. A. HAQL ATTORNEY GLOW SUPPRESSION IN INDICATOR TUBES BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to symbol indicator glow discharge tubes of the kind in which a numeral, letter or other symbol is rendered visible through an end face of the tube by glow discharge at a cathode shaped to the desired symbol. More particularly the invention is concerned with such tubes in which glow discharge cathodes, each shaped in accordance 1 with a particular symbol, are mounted one above the other inside an anode cup by means of stacks of ceramic washers spacing the cathodes from one another, leads to the cathodes being taken out through the side of the anode cup to individual base pins sealed in the tube envelope.

2. Prior Art One of the major problems in symbol indicator tubes of the above kind is to prevent glow discharge spreading to the cathode leads and becoming visible in unwanted places. An example of such a tube is found in U.S. Pat. No. 3,303,375 issued Feb. 7, 1967 and assigned to the same assignee as the instant application.

SUMMARY OF THE INVENTION In accordance with the present invention there is provided a symbol indicator glow discharge tube wherein a set of glow discharge cathodes are mounted on stacks of ceramic washers within an anode cup, the stacks being parallel to the longitudinal axis of the anode cup and adjacent the cup wall. Bare metal cathode leads to the respective cathodes are led out from at least one of the stacks through a longitudinal aperture in the cup wall radially aligned with the stack and through a common insulating disc shielding the anode cup from a set of base pins in the envelope of the discharge tube, each cathode lead being located in a respective slot in the disc and being connected to a respective one of the base pins, and a shield of insulating material interposed between the cathode leads brought out through the longitudinal aperture and the exterior wall of the anode cup, the shield being slotted for passage of the leads therethrough and extending to shield the leads against discharge between them and the anode cup. Embodiments of the invention will be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an exploded perspective view of the electrode arrangement of a discharge tube according to the present invention as would be obtained immediately prior to sealing the assembly into an envelope bulb and placing it on a pumping station for further processing before gas filling and sealing off; and

FIG. 2 is a similar view of a modified construction.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 a set of cathodes I, each in the shape of a numeral to be displayed, is mounted by means of two stacks 2 of ceramic washers within an anode cup 3. The anode cup is mounted on a valve base 4 having base pins 5 sealed therein. A tubulation 6 is provided in the base 4 for connection to an exhaust pump afier the electrode assembly and base are sealed in an envelope bulb not shown. The tubulation 6, at a later stage of manufacture, is pinched off close to the base.

The anode cup 3 is shielded from the base pins 5 within the tube envelope by means of a common insulating disc 7 of mica. Leads 8 from the individual cathodes are led out from one or other of these stacks of ceramic washers through an adrespective slots 7a in the common dlSC 7, the slots 7a ensuring that the leads are properly spaced from one another.

The shield 11 is a piece of mica sheet which extends around the anode cup 3 in the vicinity of the aperture 9 and extends from the disc 7 to near the rim of the anode cup 3. Its interposition between the exterior wall of the anode cup and the portions of leads 8 adjacent the edge of disc 7 extends the discharge path between any cathode lead and the anode and also helps to prevent emergence of ionization from the interior of the anode cup. The shield II is retained in position and curved around the adjacent portion of the anode cup by means of the cathode leads 8. In the embodiment illustrated there are two apertures 9 and hence two shields 11 through which cathode leads are brought out, but in some embodiments having fewer cathodes one position of emergence of the cathode leads may suffice.

The anode cup is closed over its upper end, through which the symbols are viewed, by means of an anode mesh 12 which fits over the central rods 13 of the stacks 2 and is secured by means of eyelets l4 and ceramic washers IS.

The embodiment of FIG. 2 is similar to that of FIG. 1 except that a further shield 16 of insulating material covers the leads 8 and is held in place by means of wire cleats l7 spot-welded onto the anode cup.

I claim:

1. A symbol indicator glow discharge tube comprising an envelope, an anode cup mounted therein and having a longitudinally apertured wall, stacks of ceramic washers positioned within said cup, a set of glow discharge cathodes mounted on said stacks, the stacks being parallel to the longitudinal axis of the anode cup and adjacent the cup wall, bare metal cathode leads connected to the respective cathodes on at least one of the stacks and passing through said longitudinal aperture in the cup wall radially aligned with the stack, a set of base pins through the envelope, a common insulating disc shielding an end of the anode cup from said base pins, each cathode lead extending from the aperture over a portion of the exterior of said cup wall and through a slot in said disc and being connected to a respective one of the base pins, and a separate shield of insulating material interposed between the extending portions of the cathode leads and the exterior wall of the anode cup adjacent said longitudinal aperture, the shield being slotted for passage of the leads therethrough and being substantially coextensive with said longitudinal aperture for preventing discharge between the extending leads and the anode cup.

2. A discharge tube as claimed in claim I wherein the shield of insulating material is a piece of mica sheet, said portions of the cathode leads extending along the outer surface of said mica sheet and retaining it in position against the curved exterior wall of said anode cup.

3. A discharge tube as claimed in claim 1 including a further shield of said insulating material adjacent the edge of said disc covering the extending cathode leads and the first mentioned shield of insulating material.

4. A discharge tube as claimed in claim 1 wherein said shield extends from said disc to the rim of said anode cup.

5. A discharge tube as claimed in claim 1 wherein said anode cup includes two apertures each having a respective shield. 

1. A symbol indicator glow discharge tube comprising an envelope, an anode cup mounted therein and having a longitudinally apertured wall, stacks of ceramic washers positioned within said cup, a set of glow discharge cathodes mounted on said stacks, the stacks being parallel to the longitudinal axis of the anode cup and adjacent the cup wall, bare metal cathode leads connected to the respective cathodes on at least one of the stacks and passing through said longitudinal aperture in the cup wall radially aligned with the stack, a set of base pins through the envelope, a common insulating disc shielding an end of the anode cup from said base pins, each cathode lead extending from the aperture over a portion of the exterior of said cup wall and through a slot in said disc and being connected to a respective one of the base pins, and a separate shield of insulating material interposed between the extending portions of the cathode leads and the exterior wall of the anode cup adjacent said longitudinal aperture, the shield being slotted for passage of the leads therethrough and being substantially coextensive with said longitudinal aperture for preventing discharge between the extending leads and the anode cup.
 2. A discharge tube as claimed in claim 1 wherein the shield of insulating material is a piece of mica sheet, said portions of the cathode leads extending along the outer surface of said mica sheet and retaining it in position against the curved exterior wall of said anode cup.
 3. A discharge tube as claimed in claim 1 including a further shield of said insulating material adjacent the edge of said disc covering the extending cathode leads and the first mentioned shield of insulating material.
 4. A discharge tube as claimed in claim 1 wherein said shield extends from said disc to the rim Of said anode cup.
 5. A discharge tube as claimed in claim 1 wherein said anode cup includes two apertures each having a respective shield. 